Time-varying network time delay compensation method of forward access of networked cascade control system (NCCS)

Abstract

The invention provides a time-varying network time delay compensation method of a forward access of a networked cascade control system (NCCS), belonging to the technical field of networked control system. In the method, a network data transmission process among forward access nodes is used instead of a network time delay compensation model among the forward access nodes so as to avoid measurement, observation, estimation or recognition of time-varying time delay when network data among the real forward access nodes are transmitted and prevent the requirements of synchronization of node clock signals. By using the method, the influence of the time-varying network time delay on the stability of a system can be reduced and the control performance quality of the system can be improved. The method is suitable for dynamic compensation and control of the time-varying network time delay when a network only exists in the forward access of the networked cascade control system under the condition that a mathematical model of a main controlled object is known or uncertainly known, a mathematical model of a vice controlled object is known, and certain interference signals exist in the system.

Description

technical field [0001] The invention relates to a compensation method for time-varying network delay in a forward path of a network cascade control system, and belongs to the technical field of network control systems. Background technique [0002] With the rapid development of computer network technology, the traditional control system is gradually replaced by the network control system. The feedback control system whose control loop is closed through the real-time network is called the networked control system (Networked control systems, NCS). Because the networked control system With outstanding features such as low cost and convenient maintenance, it has been widely used in power system, petrochemical and other industrial process control and energy transportation, environmental protection and national defense military modernization. Network control system has become a network communication and control field. research hotspots. [0003] Introducing the network into the c...

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Problems solved by technology

[0008] (2) The network delay that occurs in the process of transmitting network data from the previous node to the next node, no matter what prediction or estimation method is used in the previous node, it is impossible to know in advance the subsequent network delay Accurate value. Time delay leads to system performance degradation and even system instability, and also brings difficulties to the analysis and design of the control system.

[0013] Since the denominator of the closed-loop transfer function shown in equation (1) includes the network delay τ 1 and τ 2 index term of and The existence of time delay will deteriorate the control performance quality of the system, and even cause the system to lose stability, and in severe cases, the system may fail.

[0014] The key to reducing the impact of delay on system stability is whether the network delay τ between the main transmitter (controller) node and the auxiliary transmitter (controller) node can be realized. 1 index term of and the network delay τ between the secondary transmitter (controller) node and the actuator node 2 index term of It is removed from the denominator of equation (1), that is, the exponential term of all network delays is not included in the closed-loop characteristic equation of the system, and then the compensation of network delay is realized. However, to realize the compensation of network delay, first, Know the size of the network delay. At present, the method commonly used at home and abroad is to measure the network delay τ 1 and τ 2 measurement to compensate for the time delay τ 1 and τ 2 The impact on system stability. However, due to the network delay τ 1 and τ 2 The accurate measurement of the node needs to meet the synchronization requirements of the node clock signal. If hardware is used to realize the complete synchronization of the node clock signal, a large economic investment is required; if the software is used to correct the clock signal, the correction signal may encounter Due to the influence of network delay, it is difficult to achieve complete synchronization of node clocks; if the method of estimating, observing, identifying or predicting network delay is used to obtain the size of network delay, the accurate probability distribution of network delay must first be known, or An accurate mathematical model, but because the network delay is related to factors such as specific network protocols, network load, and network topology, there may be deviations in the estimation, observation, identification or prediction of network delay.

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